Minimally invasive surgical (MIS) instruments are often preferred over traditional open surgical devices due to the reduced post-operative recovery time and minimal scarring. Laparoscopic surgery is one type of MIS procedure in which one or more small incisions are formed in the abdomen and a trocar is inserted through the incision to form a pathway that provides access to the abdominal cavity. The trocar is used to introduce various instruments and tools into the abdominal cavity, as well as to provide insufflation to elevate the abdominal wall above the organs. The instruments and tools can be used to engage and/or treat tissue in a number of ways to achieve a diagnostic or therapeutic effect. Endoscopic surgery is another type of MIS procedure in which elongate flexible shafts are introduced into the body through a natural orifice.
Conventional MIS devices include a handle, an elongate shaft, and an end effector at the distal end for effecting tissue. Motion of the end effector is typically limited to four degrees of freedom (a degree of freedom is the direction in which the end effector can move). Furthermore, motion of the end effector reverses motion of the handle, such that the operator needs to move the handle in a direction opposite to the desired direction of movement. Shear forces on MIS instruments can also be high, leading to increased operator fatigue.
Various robotic systems have been developed to assist in MIS procedures. Robotic systems can allow for more intuitive hand movements by maintaining both natural eye-hand axis. Robotic systems can also allow for more degrees of freedom in movement by including a “wrist” joint on the instrument, creating a more natural hand-like articulation. One drawback with robotic systems, however, is the physical space required to use robotic systems during a surgical procedure and the fixed orientation of such system's robotic controls to the end effector being controlled. Another drawback is the high expense to manufacture such robotic systems.
Accordingly, there remains a need for improved methods and devices for controlling movement of a working end of an endoscopic surgical device, and in particular to methods and devices that provide for mimicking motion between an external control and an end effector.